Vibratory assembly fob



Aug. 22, 1950 e. R. MORROW 2,519,591

VIBRATORY ASSEMBLY FOR GALVANOMETERS Filed Feb. '7. 1949 73mm; 2 E

IN V EN TOR.

6. R Narrow ATTORNEY Patented Aug. 22, 1950 vmaA'roaY ASSEMBLY FOR GALvANoMn'rEas George R. Morrow, Tulsa, th., assignor to Century Geophysical Corporation, a corporation of Delaware Application February 1, 1949, Serial No. 74,940

This invention relates to improvements in galvanometers such as are used in seismograph oscillograph cameras, and the like.

Galvanometers of the type which are conventionally used in seismograph cameras include a 7 Claims. 171- 95) vibratory assembly which comprises a wire coil suspended between a pair of metallic filaments or ribbons and enclosed within a suitable housing. Such a vibrator assembly is designed to oscillate rotatively about its vertical axis in response to the passage of electric currents through the coil when the latter is subjected to the magnetic flux passing between opposed magnetic poles. A small mirror is ordinarily mounted on a part of the suspension and is designed to reflect a light beam onto a moving film in order to record the oscillations of the coil.

. Such galvanometers are ordinarily of extremely minute dimensions and it is desirable in almost all cases to provide a construction having the maximum degree of sensitivity to the actuating energy. In order to assure maximum sensitivity and eiliciency, it is highly desirable that the vibratory assembly be as nearly perfectly balanced, statically and dynamically, as possible.

In the more conventional constructions of such galvanometer assemblies, the mirror is normally mounted on the assembly by attachment to a suspension filament or to the coil and will ordinarily be disposed in a position which is displaced or off-set from the axis of oscillation of the assembly. Since the mirror, although very small, will have substantial mass, as compared with the remainder of the assembly, it will ordinarily create a condition of unbalance in the assembly which must be effectively counter-balanced, as by providing a suitable counter-balancing mass in an appropriate position on the assembly. This necessarily involves additional parts, expense and efiort in construction and in adjustment of the vibratory assembly and reduces the electrical efllciency of the galvanometer, especially where electrico-magnetic damping is used.

Accordingly, it is a principal object of this invention to provide an improved form of galvanometer assembly constructed to provide improved static and dynamic balance therein.

Another object is to provide a galvanometer construction in which the mirror is symmetrically disposed about the axis of oscillation of the galvanometer.

Still another obiect is to provide an improved suspendingconnection between the coil and the suspension filaments in which the mirror is en- 2 closed in alignment with the axis of oscillation of the galvanometer.

Other and more specific objects and advantages of this invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings which illustrate a useful embodiment in accordance with this invention.

In the drawings:

Fig. 1 is a front elevational view of a galvanometer vibratory assembly in accordance with this invention;

Fig. 2 is a cross-sectional view along line 2-2 of Fig. 1;

Fig. 3 is a side elevational view of the structure shown in Fig. 1;

Fig. 4 is a front elevational view of the mirror supporting element adapted to connect the coil to the upper suspension element of the galvanometer;

Fig. 5 is a side view or the element shown in Fig.

Figs. 6 and 7 are front and side elevational views of a modified connection element adapted for connecting the lower suspension filament to the lower end of the coil;

Fig. 8 is a side elevational view of one of the spools on which the galvanometer coil is wound;

Fig. 9 is an end view of the spool shown in Fig. 1; and

Fig. 10 is a fragmentary view illustrating another embodiment of the spool shown in Figs. 7 and 8.

Referring to the drawings: The galvanometer assembly comprises an elongated coil l0 comprising a number'of turns of very fine wire wound over a pair of spools, indicated generally by the numerals lI-l l. A generally U-shaped connector 0r clevis, indicated generally'by the numeral l2, connects spool H at the upper end of the coil to an upper metallic suspension filament or ribbon iii. A mirror i4 is enclosed within the arms of clevis l2 above the coil. A second U- shaped connector or clevis l5 connects the lower spool II to a lower suspension filament or ribbon I 6. This assembly will ordinarily be mounted in a suitable casing (not shown) in any suitable manner, as. shown. for example, in Marvin E. Morrow Patent No. 2,439,576, April 13, 1948. In such galvanometers. coil III will normally be suspended in a magnetic gap where it will be subject in the usual manner to magnetic flux pass- 7 ing therethrongh.

prises a cylindrical central portion l1 about which the coil is wound and having end flanges l8ll and cylindrical trunnions l9 extending outwardly from flanges i8. The spools may be provided with an axial aperture 20. Upper connector or clevis I2 (Figs. 4 and 5) consists of a U-shaped element having elongated arms 2l2l constructed generally of a strip of electrically conducting metal. The ends of the arms are provided with eyes 22 in which trunnions I 9 are adapted to be joumalled. The'base Or curved end portion of the clevis may be provided with flanges 23-23 extending laterally from opposite edges thereof to stiffen or reinforce the connector at this point. The upper suspension filament or ribbon I3 is attached to connector l2 by looping an end of the ribbon about the base portion of the connector and soldering the loop to form a permanent connection between the filament and the connector, as illustrated particularly in Figs. 1 and 3. Mirror I 4 is inserted between arms 2| of the clevis i2 and will ordinarily be of flat rectangular shape adapted to fit snugly between the arms and will ordinarily be held in place by cementing the edges of the mirror to the adjacent fiat inner faces of arms 2|. Lower connector I! (Figs. 6 and 7) is likewise a U-shaped elementconstructed of a strip of fiat electrically conducting metal having arms 25-25 provided at their ends with eyes 26 for receiving the trunnions IS on lower spool ll. Lower suspension filament I 6 will be connected to the base portion of clevis IS in the same manner as upper filament i3 is connected to the upper connector l2, as described above.- The opposite ends of coil ill will be connected to the respective connectors l2 and II at 21 and 28 respectively.

As illustrated particularly in Figs. 1, 2 and 3, it will be seen that the arrangement of mirror It between arms 2| of the upper connector is such that its plane will lie generally in a vertical plane passing transversely through the center of the vibratory assembly and that the axis of oscillation of the assembly will pass vertically through the mirror.

By reason of this construction, it will be seen that mirror I 4 will now be disposed symmetrically about the axis of oscillation of the vibratory assembly and the vibratory assembly will be substantially balanced, both statically and dynamically.

Trunnions It will ordinarily be made of a length, so related to the thickness of the metal strips forming the clevises, that when inserted in eyes 22 and 26, respectively, the outer ends of the trunnions will be flush with the outer faces of arms 2| and 25, respectively. This arrangement will generally permit narrowing the dimensions of the assembly as a whole, thereby permitting corresponding narrowing of the flux gap in which the coil will be installed, and thereby increasing the sensitivity of the galvanometer.

Fig. 10 illustrates another embodiment of the spool construction in which trunnions l9 are provided with inwardly tapering or under-cut peripheral surfaces 30, which will assist in holding the connectors in place on the spools, since the vibrations of the assembly would tend to urge the clevis arms along the tapering surfaces inwardly against flanges l8.

It will be understood that various changes and alterations may be made in the details of the illustrative embodiment without departing from the scope of the appended claims but within the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

l. A vibratory assembly for galvanometers, comprising, a coil, a pair of suspension elements attachable to opposite ends of the coil, generally U-shaped connector members connecting the ends oiksaid coil to said suspension elements, the ends of said coil being supported between the arms of the respective connector members, and a mirror mounted between the arms of one of said connector members and symmetrically arranged therein with respect to the longitudinal axis of said assembly.

2. A vibratory assembly for galvanometers comprising, a coil, a pair of spaced spools about which said coil is wound, said spools extending transversely of said coil, a pair of suspension elements attachable to opposite ends of said coil. connector members for connecting said suspension elements to said coil, at least one of said connector members being of generally U-shape having its base portion connected to one of said suspension elements and its arms connected to opposite ends of one of said spools, and a mirror mounted between said arms symmetrically with respect to the longitudinal axis of said assembly.

3. A vibratory assembly for galvanometers comprising, a coil, a pair of spaced spools about which said coil is wound, said spools extending transversely of said coil and having trunnion members extending laterally from the ends thereof, a pair of suspension elements attachable to opposite ends of said coil, connector members for connecting said suspension elements to said coil, at least one of said connector members being of generally U-shape having its base portion connected to one of said suspension elements and having apertures in the ends of its arms in which said trunnions are insertible, and a mirror mounted between said arms symmetrically with respect to the longitudinal axis of said assembly.

4. A vibratory assembly in accordance with claim 3 in which said one of said connector members is constructed of fiat strip metal.

5. A vibratory assembly in accordance with claim 3 in which said one of said connector members is constructed of fiat strip metal, the base portion of said connector member having a pair of stiffening flanges extending laterally outwardly from the opposite edges thereof.

6. A vibratory assembly in accordance with claim 3 in which said one of said connector members is constructed of flat strip metal, and said mirror is of flat generally rectangular shape having its side edges attached to the opposed flat faces of the arms of said connector members.

7. A vibratory assembly for galvanometers, comprising, a coil, a pair of suspension elements attachable to opposite ends of the coil, connector members for connecting said suspension elements to said coil, at least one oi said connector members being 01' generally U-shape and supporting an end of the coil between the arms thereof, and a mirror mounted between said arms symmetrically with respect to the longitudinal axis of said assembly.

GEORGE R. MORROW.

REFERENCES CITED UNITED STATES PATENTS Name Date Morrow Apr. 13, 1948 Number 

